1. Field of the Invention
The present invention relates to the field of power circuits and particularly to an uninterruptable power supply (UPS) inserted between a source of AC power and a load such as a computer monitor or other computer peripherals designed to supply power to the load in the event the source of AC power should be interrupted for some predetermined period of time. This concept provides for a UPS unit inserted between a source of AC line power and its load in order to draw only a fixed amount of power from the AC power source.
2. Description of Prior Art
There are a great number of uninterruptable power supplies on the market today and can be divided into two basic types. The first type of circuit continues to supply power when the power fails. The second type of circuit supplies the power continuously to a selected load from a battery which is continuously charged while the power line signal is present. With this circuit, no switching is required. The latter type is not as efficient as the former since it must operate continuously whereas the former type draws power directly from the power line unless there is a failure. A third type of uninterruptable power supply is disclosed in U.S. Pat. No. 5,737,209, issued on Apr. 7, 1998, wherein a direct current output is presented to the load by the uninterruptable supply.
Therefore, a need has existed to provide a UPS circuit to a load when no interruption from an AC source is present when the load requires more power than a predetermined amount.
The subject invention deals with the second type of uninterruptable supply noted above which provides a circuit having a limit on the amount of power that can be drawn from an AC power line forcing a battery to supply that additional power whenever power it is needed and allowing the battery or batteries to be recharged when the power from the line is not needed.
Therefore, it is an object of this invention to control the amount of energy that is drawn from a AC power source such that it will not exceed a predetermined amount.
Another object of the invention is to incorporate changes in existing UPS devices to accomplish a peak energy control.
Yet another object in this invention is to do all of these things in a manner that is economical and that would be commercially accepted